In order to use the original Masm64 SDK, you need the ML64 and link binaries. Here is a program that allows to install them from known Microsoft locations. Extract all files to a folder on your Masm drive, then run GrabBin64.exe.
The smallprint:
Use at your own risk. The downloads may be copyrighted, or you may need a Visual Studio license to use them.
(http://www.jj2007.eu/pics/GrabBin64.png)
Feedback is welcome btw - firewall problems etc, bugs, crashes anybody?
Updated links attached.
Works. Thanks.